Those defensive backs invited to the combine workouts arrived in Indianapolis on Saturday, and team scouts, coaches and medical personnel will begin poking and probing them today.

The Steelers will have a front-row seat and will pay close attention when they parade the safety candidates around the room.

No team had stronger safeties than did the Steelers in 2011 when Troy Polamalu made his annual trip to the Pro Bowl following that season and Ryan Clark joined him for the first time.

A year later, neither made it to the all-star game, and this year Polamalu will be 32 years old and Clark 34. It's time for the Steelers to find their replacements.

Clark enters the final season of his contract and while he played at a Pro Bowl level last season, he's not getting any younger. Polamalu, on the other hand, is not getting any healthier. He missed nine games with a calf injury last season and has missed 22 over the past four seasons with injuries.

Clark has improved annually. He calls the signals in the secondary and has become one of their true bargain free-agent finds, having joined them in 2006 to replace Chris Hope, who left as a free agent to sign with Tennessee. Unlike Polamalu, he has been an ironman. The only games Clark has missed over the past four seasons were those played in Denver for precautionary health reasons related to his previous near-fatal physical reaction playing there because of his sickle cell trait.

The Steelers' top backups at safety, veterans Will Allen and Ryan Mundy, are both unrestricted free agents. Mundy took over for an injured Polamalu in the second and third games last season, but the coaches switched to Allen after that because they were not satisfied with Mundy's play. Allen started the next seven games in which Polamalu did not play. Allen will be 31 and Mundy is 28.

They have two young safeties who have potential but would not be considered an heir apparent at this point.

Robert Golden made the team as an undrafted rookie last season. Damon Cromartie-Smith spent most of the past two seasons on the Steelers practice squad, elevated to the roster for four games in 2011 and two games in 2012.

Kenny Vaccaro of Texas appears to be the only prospect as a first round choice two months before they actually start drafting. However, there should be decent safeties available in the second and third rounds.

Cornerback had been the weakest position for the Steelers through the years with Ike Taylor the lone exception. They ran through a gaggle of left cornerbacks until Keenan Lewis finally surfaced in his fourth season to give them their best play on that side in years. Lewis led the league, according to ProFootballFocus.com, with 16 passes broken up. Coupled with the emergence of Cortez Allen as a strong nickel back, the cornerback position was in good hands with those three.

Now Lewis is an unrestricted free agent and if the Steelers do not re-sign him, Allen will take over at left cornerback and Curtis Brown will move up a notch. With Taylor out for the final four games with an ankle injury, the Steelers generally went with Allen at right cornerback with Brown moving there and Allen moving to the slot in the nickel defense.

DeMarcus Van Dyke, claimed off waivers by the Steelers from Oakland to start the season, and Josh Victorian are two young cornerbacks who will add depth and perhaps push Brown for his No. 3 spot. They also re-signed veteran Justin King.

The draft is top-heavy with cornerbacks with as many as four projected to go in the first round and perhaps nine in the first two rounds.

The secondary was a big reason the Steelers had the NFL's No. 1 pass defense, allowing just 185.2 yards passing per game. That was more impressive because both sacks and quarterback pressures were down. The secondary needs to improve its play-making because they managed only six of the team's 10 interceptions with Clark and Cortez Allen getting two apiece. As a team, the Steelers ranked 27th in the NFL in percentage of passes intercepted.

It is a secondary worthy of a championship team, provided Polamalu can stay healthy, and it will remain stronger if they are able to find a way to pay Lewis and keep him.

Even if Lewis leaves, the Steelers will not be pressured to pick another cornerback high in the draft because of the depth they have developed at the position the past few years. Their primary need in the secondary is to develop the next Clark and/or Polamalu and they have the luxury of not force-feeding a rookie if they do draft one unless injuries become a problem again. Even Polamalu did not start as a rookie.

If we can't get an OLB...have to draft safety in 1st round and a corner in the 2nd...I'm thinking Lewis might not come back...whoever they draft in the first 2 rounds has to make an impact on the team almost immediately...